In general, to perform a cutting operation or a polishing operation, particles having excellent abrasion resistance such as diamond particles, carbide, boric acids, nitrides, hard metal and ceramic pieces may be used. Among these, diamonds are well-known as being the hardest substances on Earth, and have been widely used for a cutting tool or a grinding (polishing) tool due to this fact.
Typically, a diamond tool configured as segments may include a cutting/polishing segment (cutting tip) on which the diamond particles are distributed, and a metal body (tool body or shank) to which the cutting/polishing segment is fixed.
FIG. 1 is a view showing examples of various types of diamond tools configured as segments. As shown in FIG. 1 (a), a saw blade 10a configured as segments includes a plurality of segments 12a (cutting tips) that are fixed to a disk shaped-metal body 11a. A core bit 10b configured as segments, as shown in FIG. 1(b), includes a plurality of segments 12b (cutting tips) that are fixed to a metal body 11b, and a polishing wheel 10c configured as segments, as shown in FIG. 1(c), includes a plurality of segments 12c (polishing tips) that are fixed to a bottom surface of a metal body 11c. As for the above described segments 12a, 12b, and 12c of the cutting/polishing tools 10a, 10b, and 10c, diamond particles (D) are randomly distributed between metal powders (bond metal)(M), and the diamond particles distributed in each segment may perform a cutting/polishing operation.
To manufacture the above described cutting/polishing segment, a powder metallurgy scheme may be generally used. Specifically, metal powder and diamond particles (crystals) are mixed, and the mixture is molded into a cutting/polishing segment shaped-form. Then, the obtained molding is heated to a high temperature to form the cutting/polishing segment with dense tissue through a sintering scheme or a hot pressing scheme. Thereafter, the cutting/polishing segment is bonded to the tool body (shank), and in this bonding process, a laser welding, a brazing using a silver solder, a diffusion bonding using sintering, and the like may be used. However, the above described tool manufacturing method may have many problems in that a complex process such as sintering and the like may be required for manufacturing the cutting/polishing segment, and an additional process such as a welding operation, or the like, may be required for fixing the cutting/polishing segment to the tool body, and therefore many processes and facilities may be required for manufacturing the cutting/polishing tool, and much labor may be also required.
In order to overcome these problems, there is disclosed Korean Patent No. 452563 (U.S. Pat. No. 6,316,065) directed to a manufacturing method for a cutting tool using a laser cladding technology.
As shown in FIG. 2(a), in a manufacturing method for a cutting tool disclosed in Korean Patent No. 452563, a mixed powder of the metal powder (M) and the diamond particles (D) may be sprayed using a powder supplying device 30 while heating an outer surface 11a of a tool body 11 using a laser heating device 20, and the mixed powder of the metal powder (M) and the diamond particles (D) may be deposited on the outer surface 11a of the tool body 11 to form a cutting body 12. In this instance, while the cutting body 12 is formed on the tool body 11 of the cutting tool, the tool body 11 may be moved to a direction (X) opposite to a gravity direction (G), and an angle (±w) between the gravity direction (G) and a line perpendicular to a section (S) where the deposition is performed by a laser heating device 20 may be maintained in a range of 60 degrees to 90 degrees for a time period during which the mixed powder is clotted. Also, as shown in FIG. 4, even in a case of forming a cutting body 12′ on an outer surface 11a′ while rotating a disk-shaped tool body 11′, the angle (±w) between the gravity direction (G) and the line perpendicular to the section (S) where the deposition is performed may be maintained in the range of 60 degrees to 90 degrees for the time period during which the mixed powder is clotted.
As described above, the manufacturing method for the cutting tool shown in FIG. 2(a) and FIG. 4 may allow the cutting tool to be manufactured through a single process by laser-cladding the metal powder (M) and the diamond particles (D) directly onto the tool bodies 11 and 11′, and thereby may improve productivity and reduce manufacturing costs. Also, in the case of sintering the cutting/polishing segment, a mechanical bond between the diamond particles and the metal powder is achieved, however, in a case of using the laser cladding technology, a chemical bond between the diamond particles and the metal powder is achieved and thus, the manufacturing method may improve an adhesion and a quality of the tool thereby.
In addition, as for the manufacturing method for the cutting tool disclosed in the above Korean Patent, since the tool body 11 may be moved in the direction (X) opposite to the gravity direction (G) while being heated in a practically horizontal direction using the laser heating device 20, there is an advantage in that a distribution range of the diamond particles (D) is relatively widened in comparison with the related art (background art of the Korean Patent No. 452563) where heat is applied from an upper side of the tool body 11.
Meanwhile, in the case of manufacturing the cutting tool using the laser cladding process, a melting and a clotting momentarily occur in an area where a laser beam is radiated, however, the diamond particles may be moved in the direction opposite to the gravity direction, due to a specific gravity difference between the diamond particles and a melted metal powder, even in the short period of time.
Specifically, referring to FIG. 2(b), an oval shaped-molten pool may be generated on a processing part of the cutting body 12 corresponding to a section (S) where the laser beam is radiated, by a transfer speed of the tool body 11 and a radiation direction of the laser beam, and the diamond particles (D) may be momentarily moved to a top end of the molten pool due to a specific gravity lower than a specific gravity of the molten metal powder (M). Specifically, the diamond particles (D) may be densely located in a part of the oval-shaped molten pool that is far from the outer surface 11a of the tool body 11.
Consequently, in the manufacturing method for the cutting tool disclosed in the Korean Patent, since the diamond particles (D) are densely located only in an outer surface side of the cutting body 12 as shown in FIG. 3, the diamond particles (D) are not uniformly distributed throughout the entire cutting body 12 and thus, the efficiency of the cutting tool may not be uniformly achieved, and the cutting body 12 may not be used as a whole.
Also, in the manufacturing method for the cutting tool disclosed in the Korean Patent, there is a problem in that since the diamond particles (D) are densely located on the outer surface side of the cutting body 12, that is, the outer surface, an additional laser cladding process may not be performed in a part of the previouslyformed cutting body 12. That is, in a case of melting the outer surface of the previously formed cutting body 12 by repeatedly applying heat to the outer surface of the previously formed cutting body 12, the cutting performance of the diamond particles may be degraded and oxidation of the diamond particles may be easily generated due to properties of the diamond particles that are susceptible to heat. In addition, since the metal powder (M) restraining the diamond particles (D) may be re-melted, restraints on the diamond particles (D) may be released, so that the deposited diamond particles may be floating so as to be densely located in the outer surface side of the molten pool. As a result, it is difficult to perform laser cladding processes multiple times.